1. Field of the Invention
The present invention relates to a high-frequency module including internal electrodes and via electrodes connected to ground and a high-frequency circuit element provided inside a laminate substrate including a plurality of base materials laminated on each other.
2. Description of the Related Art
A high-frequency module is configured by mounting active elements, passive elements, or wiring configuring a high-frequency circuit inside a laminate substrate or on a top surface of the laminate substrate. The laminate substrate is configured by laminating a plurality of base materials, providing an internal electrode between layers, and providing via electrodes penetrating inside the layers (For example, see JP 06-52191 Y).
FIG. 6 is a perspective view of a laminate substrate which configures a high-frequency module according to a related art example.
A laminate substrate 101 illustrated in FIG. 6 includes a laminate 102 including a plurality of base materials, an internal electrode 103 for grounding provided between layers of the laminate 102, and via electrodes 104 for grounding provided inside the layers of the laminate 102. The internal electrode 103 is endlessly provided along an outer edge of the laminate 102 as viewed in a lamination direction (hereinafter, the outer edge as viewed in the lamination direction will be referred to simply as the “outer edge”). The via electrodes 104 are closely arrayed along the outer edge of the laminate 102 and connect together the internal electrodes 103 facing each other. Therefore, the laminate substrate 101 obtains a shield property against high-frequency noise at the outer edge of the laminate 102 by the internal electrodes 103 for grounding and the via electrodes 104 for grounding.
In the high-frequency module according to the related art example, since the internal electrodes 103 for grounding are provided along the outer edge of the laminate 102, the thickness on a periphery of the outer edge of the laminate 102 increases by the thicknesses of the internal electrodes 103. Additionally, since a thickness shrinkage of the laminate 102 generated during manufacturing becomes small around the via electrodes, the thickness on the periphery of the outer edge of the laminate 102 is greatly different from the thickness of a central portion thereof in a case where the number of the via electrodes 104 for grounding is large. Therefore, in order to mold the laminate 102 with high flatness, it is desirable that the number of the layers of the laminate 102, the number of the internal electrodes 103, and the number of the via electrodes 104 be smaller.
However, in the high-frequency module according to the related art example, since the internal electrodes 103 are provided along the entire periphery of the outer edge on all of the layers of the laminate 102, area other than the internal electrode 103 is small and area utilization efficiency is low. Therefore, in order to realize a complicated wiring structure where many active elements or passive elements are mounted in the laminate 102, it has been difficult to reduce the number of the layers of the laminate 102 and the number of the internal electrodes 103.
Moreover, the internal electrode 103 is provided in such a manner that the entire length thereof is almost the same as the entire length of the outer edge of the laminate 102. Accordingly, in a case where the number of the via electrodes 104 is reduced, the internal electrodes 103 become inductive and a potential difference from ground potential is generated in the internal electrodes 103, thereby deteriorating high-frequency properties. Therefore, in order to prevent deterioration of the high-frequency properties, it has been difficult to reduce the number of the via electrodes 104.
In this way, in the high-frequency module 101 according to the related art example, in order to secure the complicated wiring structure or the good high-frequency properties, the number of the layers of the laminate 102, the number of the internal electrodes 103, or the number of the via electrodes 104 cannot be reduced, and it has been difficult to realize high flatness.
Furthermore, in the laminate substrate 101 according to the related art example, since metallic density in the vicinity of the outer edge of the laminate 102 is high, permeation of gas (outgassing) emitted from internal residues during manufacturing is hindered, and delamination is easily generated between the layers of the laminate 102, thereby also causing a problem of lowering reliability.